The present invention relates to a resilient shaft coupling having two metal parts, one of which can be connected to an input, the other to an output, with torque being adapted to be transmitted between these parts via a number of circumferentially consecutive resilient coupling members that are made of rubber or the like; the metal parts comprise an inner coupling ring and, coaxial thereto, an outer coupling ring, with those generated surfaces of the rings that face one another having formed therein a number of alternately interengaging (in the circumferential direction) and substantially radially extending cams, dogs, or teeth that extend over the axial length of the coupling rings and to a location near the pertaining opposite generated surface; each two circumferentially consecutive cams or dogs form a pair whose facing surfaces are concave and delimit a chamber, the longitudinal axis of which extends parallel to the rotational axis; a resilient coupling member is disposed in the chamber, with the shape of the resilient coupling members before installation being substantially that of a circular rod of a length corresponding substantially to the axial length of the coupling rings; upon installation, the resilient coupling members are subjected to a predetermined radial loading.
Resilient shaft couplings wherein the torque is transmitted between circular coaxial coupling hubs that have interengaging cams, dogs, or teeth via a number of circumferentially consecutive resilient rubber coupling members are known in a variety of constructions as so-called positive or dog couplings; the basic constructon thereof is disclosed by German Auslegeschrift No. 10 67 644 Croset dated Oct. 22, 1959, corresponding to U.S. Pat. No. 2,873,590-Croset dated Feb. 17, 1959.
In this known coupling, chambers are provided each being adapted to receive a circular-section rubber coupling member disposed between every two adjacent cams or dogs; the chambers are of a size and design such that, with the coupling unloaded, the resilient coupling member in the chamber does not contact the cams or dogs that delimit the latter, i.e., each individual resilient coupling member extends in the circumferential direction with a reduced clearance between the cams or dogs. Consequently, when a torque is applied to the coupling, its torsional stiffness near its neutral point is undefined, but once the reduced clearance has been taken up, and the resilient coupling members experience compression, torsional stiffness rises very rapidly to high values as torque continues to be applied.
In a coupling system of this type, it is impossible to provide low defined levels of torsional stiffness in the low-torque range after the clearance has been taken up. The result of this, for example in vehicle drives having a combustion engine, is the typical "transmission clatter" associated with starting at a low speed.
It is an object of this invention to improve the design of a resilient shaft coupling of the positive type in such a way that its torsional stiffness is very reduced at low torques, that it retains this low torsional stiffness at zero average useful torque, and that it operates in this condition without clearance and without any impairment of torsional stiffness at full load as compared with known resilient positive couplings that have intermediate resilient coupling members. Furthermore, the novel resilient shaft coupling is intended to be highly reliable in operation, to require little servicing, and to be able to be manufactured economically.